Since Crohn's original description,1 the histopathologic criteria for the diagnosis of regional enteritis have not been conspicuously altered. Despite technical refinements and search for specificity of various histologic parameters2-9 in the disease, it may be said that there are no pathognomonic features in regional enteritis. This is predicated upon the following: (1) the small intestine has, in the majority of instances, a restricted mode of reactivity to various and diverse agents; (2) regional enteritis is a progressive disease with a fluidity of transition between various histopathologic changes; and (3) the appearance of the intestine, at any given time during the clinical course of the disease, is a composite of "primary" and "secondary" reactions with obscuration of the primary lesion by the latter in the progression of biologic time.5

The sequence of morphologic changes occurring in regional enteritis may then be considered to represent a spectrum with considerable